Measurement of total pulmonary arterial compliance using invasive pressure monitoring and MR flow quantification during MR-guided cardiac catheterization

1 Cardiac MR Research Group, Division of Imaging Sciences, King’s College London; 2 Department of Congenital Heart Disease, Guy’s Hospital; and 3 Cardiothoracic Unit, Institute of Child Health and Great Ormond Street Hospital, London, United Kingdom Submitted 13 September 2004 ; accepted in final form 18 April 2005 Pulmonary hypertensive disease is assessed by quantification of pulmonary vascular resistance. Pulmonary total arterial compliance is also an indicator of pulmonary hypertensive disease. However, because of difficulties in measuring compliance, it is rarely used. We describe a method of measuring pulmonary arterial compliance utilizing magnetic resonance (MR) flow data and invasive pressure measurements. Seventeen patients with suspected pulmonary hypertension or congenital heart disease requiring preoperative assessment underwent MR-guided cardiac catheterization. Invasive manometry was used to measure pulmonary arterial pressure, and phase-contrast MR was used to measure flow at baseline and at 20 ppm nitric oxide (NO). Total arterial compliance was calculated using the pulse pressure method (parameter optimization of the 2-element windkessel model) and the ratio of stroke volume to pulse pressure. There was good agreement between the two estimates of compliance ( r = 0.98, P < 0.001). However, there was a systematic bias between the ratio of stroke volume to pulse pressure and the pulse pressure method (bias = 61%, upper level of agreement = 84%, lower level of agreement = 38%). In response to 20 ppm NO, there was a statistically significant fall in resistance, systolic pressure, and pulse pressure. In seven patients, total arterial compliance increased >10% in response to 20 ppm NO. As a population, the increase did not reach statistical significance. There was an inverse relation between compliance and resistance ( r = 0.89, P < 0.001) and between compliance and mean pulmonary arterial pressure ( r = 0.72, P < 0.001). We have demonstrated the feasibility of quantifying total arterial compliance using an MR method. pulmonary hypertension; nitric oxide; magnetic resonance imaging Address for reprint requests and other correspondence: R. Razavi, 5th Floor, Guy’s Hospital, London SE1 9RT, UK (E-mail: reza.razavi{at}kcl.ac.uk )